Wavelength-Gated Photochemical Synthesis of Phenalene Diimides.
Ontology highlight
ABSTRACT:
SUBMITTER: Feist F
PROVIDER: S-EPMC8251713 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Asymmetric photochemical synthesis using circularly polarized (CP) light is theoretically attractive as a means of absolute asymmetric synthesis and postulated as an explanation for homochirality on Earth. Using an asymmetric photochemical synthesis of a dihydrohelicene as an example, we demonstrate the principle that two wavelengths of CP light can be used to control separate reactions. In doing so, a photostationary state (PSS) is set up in such a way that the enantiomeric induction intrinsic to each step can combine additively, significantly increasing the asymmetric induction possible in these reactions. Moreover, we show that the effects of this dual wavelength approach can be accurately determined by kinetic modelling of the PSS. Finally, by coupling a PSS to a thermal reaction to trap the photoproduct, we demonstrate that higher enantioselectivity can be achieved than that obtainable with single wavelength irradiation, without compromising the yield of the final product.
| S-EPMC5707454 | biostudies-other
Project description:Predicting the conversion and selectivity of a photochemical experiment is a conceptually different challenge compared to thermally induced reactivity. Photochemical transformations do not currently have the same level of generalized analytical treatment due to the nature of light interaction with a photoreactive substrate. Herein, we bridge this critical gap by introducing a framework for the quantitative prediction of the time-dependent progress of photoreactions via common LEDs. A wavelength and concentration dependent reaction quantum yield map of a model photoligation, i.e., the reaction of thioether o-methylbenzaldehydes via o-quinodimethanes with N-ethylmaleimide, is initially determined with a tunable laser system. Combined with experimental parameters, the data are employed to predict LED-light induced conversion through a wavelength-resolved numerical simulation. The model is validated with experiments at varied wavelengths. Importantly, a second algorithm allows the assessment of competing photoreactions and enables the facile design of λ-orthogonal ligation systems based on substituted o-methylbenzaldehydes.
| S-EPMC7966369 | biostudies-literature
Project description:We exploit the wavelength dependence of [2 + 2] photocycloadditions and -reversions of styrylpyrene to exert unprecedented control over the photoreversible polymerization and topology of telechelic building blocks. Blue light (λ max = 460 nm) initiates a catalyst-free polymerization yielding high molar mass polymers (M n = 60 000 g mol-1), which are stable at wavelengths exceeding 430 nm, yet highly responsive to shorter wavelengths. UVB irradiation (λ max = 330 nm) induces a rapid depolymerization affording linear oligomers, whereas violet light (λ max = 410 nm) generates cyclic entities. Thus, different colors of light allow switching between a depolymerization that either proceeds through cyclic or linear topologies. The light-controlled topology formation was evidenced by correlation of mass spectrometry (MS) with size exclusion chromatography (SEC) and ion mobility data. Critically, the color-guided topology control was also possible with ambient laboratory light affording cyclic oligomers, while sunlight activated the linear depolymerization pathway. These findings suggest that light not only induces polymerization and depolymerization but that its color can control the topological outcomes.
| S-EPMC7069517 | biostudies-literature
Project description:In Photosystem I (PS I) long-wavelength chlorophylls (LWC) of the core antenna are known to extend the spectral region up to 750 nm for absorbance of light that drives photochemistry. Here we present clear evidence that even far-red light with wavelengths beyond 800 nm, clearly outside the LWC absorption bands, can still induce photochemical charge separation in PS I throughout the full temperature range from 295 to 5 K. At room temperature, the photoaccumulation of P700(+•) was followed by the absorbance increase at 826 nm. At low temperatures (T < 100 K), the formation of P700(+•)FA/B(-•) was monitored by the characteristic EPR signals of P700(+•) and FA/B(-•) and by the characteristic light-minus-dark absorbance difference spectrum in the QY region. P700 oxidation was observed upon selective excitation at 754, 785, and 808 nm, using monomeric and trimeric PS I core complexes of Thermosynechococcus elongatus and Arthrospira platensis, which differ in the amount of LWC. The results show that the LWC cannot be responsible for the long-wavelength excitation-induced charge separation at low temperatures, where thermal uphill energy transfer is frozen out. Direct energy conversion of the excitation energy from the LWC to the primary radical pair, e.g., via a superexchange mechanism, is excluded, because no dependence on the content of LWC was observed. Therefore, it is concluded that electron transfer through PS I is induced by direct excitation of a proposed charge transfer (CT) state in the reaction center. A direct signature of this CT state is seen in absorbance spectra of concentrated PS I samples, which reveal a weak and featureless absorbance band extending beyond 800 nm, in addition to the well-known bands of LWC (C708, C719 and C740) in the range between 700 and 750 nm. The present findings suggest that nature can exploit CT states for extending the long wavelength limit in PSI even beyond that of LWC. Similar mechanisms may work in other photosynthetic systems and in chemical systems capable of photoinduced electron transfer processes in general.
| S-EPMC3959156 | biostudies-literature
Project description:The control of chemical functionalization with orthogonal light stimuli paves the way toward manipulating materials with unprecedented spatiotemporal resolution. To reach this goal, we herein introduce a photochemical reaction system that enables two-color control of covalent ligation via an oxo-Diels-Alder cycloaddition between two separate light-responsive molecular entities: a UV-activated photocaged diene based on ortho-quinodimethanes and a carbonyl dienophile appended to a diarylethene photoswitch, whose reactivity can be modulated upon illumination with UV and visible light.
| S-EPMC8483443 | biostudies-literature
Project description:Methylated polycyclic aromatic hydrocarbons (PAHs) are suspected to be some of the toxic compounds in crude oil towards marine life and are needed as single compounds for environmental studies. 1-, 3- and 6-methylchrysene (3a,b,c) were prepared as single isomers by photochemical cyclization of the corresponding stilbenoids in the Mallory reaction using stoichiometric amounts of iodine in 82-88% yield. 2-methylchrysene (3d) was prepared by photochemical cyclization where the regioselectivity was controlled by elimination of an ortho-methoxy group under acidic oxygen free conditions in 72% yield. These conditions failed to form 4-methylchrysene from the corresponding stilbenoid. All stilbenoids were made from a common naphthyl Wittig salt and suitably substituted benzaldehydes. We have also demonstrated that methylchrysenes can be oxidized to the corresponding chrysenecarboxylic acids by KMnO4 in modest yields.
| S-EPMC9822284 | biostudies-literature
Project description:The evolution of a variety of important chromophore-dependent biological processes, including microbial light sensing and mammalian color vision, relies on protein modifications that alter the spectral characteristics of a bound chromophore. Three different color opsins share the same chromophore, but have three distinct absorptions that together cover the entire visible spectrum, giving rise to trichromatic vision. The influence of opsins on the absorbance of the chromophore has been studied through methods such as model compounds, opsin mutagenesis, and computational modeling. The recent development of rhodopsin mimic that uses small soluble proteins to recapitulate the binding and wavelength tuning of the native opsins provides a new platform for studying protein-regulated spectral tuning. The ability to achieve far-red shifted absorption in the rhodopsin mimic system was attributed to a combination of the lack of a counteranion proximal to the iminium, and a uniformly neutral electrostatic environment surrounding the chromophore.
| S-EPMC4104663 | biostudies-literature
Project description:11,12-Dihydrodibenzo[c,g]-1,2-diazocines have been established as a viable alternative to azobenzene for photoswitching, in particular, as they show an inverted switching behavior: the ground state is the Z isomer. In this paper, we present an improved method to obtain dibenzodiazocine and its derivatives from the respective 2-nitrotoluenes in two reaction steps, each proceeding in minutes. This fast access to a variety of derivatives permitted the study of substitution effects on the synthesis and on the photochemical properties. With biochemical applications in mind, methanol was chosen as a protic solvent system for the photochemical investigations. In contrast to the azobenzene system, none of the tested substitution patterns resulted in more efficient switching or in significantly prolonged half-lives, showing that the system is dominated by the ring strain.
| S-EPMC8296553 | biostudies-literature
Project description:Responsive materials, such as switchable hydrogels, have been largely engineered for maximum changes between two states. In contrast, adaptive systems target distinct functional plateaus between these maxima. Here, we demonstrate how the photostationary state (PSS) of an E/Z-arylazopyrazole photoswitch can be tuned by the incident wavelength across a wide color spectrum, and how this behavior can be exploited to engineer the photo-dynamic mechanical properties of hydrogels based on multivalent photoswitchable interactions. We show that these hydrogels adapt to the wavelength-dependent PSS and the number of arylazopyrazole units by programmable relationships. Hence, our material design enables the facile adjustment of the mechanical properties without laborious synthetic efforts. The concept goes beyond the classical switching from state A to B, and demonstrates pathways for a truly wavelength-gated adaptation of hydrogel properties potentially useful to engineer cell fate or in soft robotics.
| S-EPMC7898538 | biostudies-literature
Project description:In this paper, the structural and photochemical properties of a monolithic photochemical diode are discussed. The present structure is composed, from the top to the bottom, of a TiO2 nanowire layer, a TiO2 film, a Ti foil, and a porous layer made of Pt nanoparticles. The synthesis of the nanowires was simply carried out by Au-catalysed-assisted process; the effects of the annealing temperature and time were deeply investigated. Morphological and structural characterizations were performed by scanning electron microscopy and Raman spectroscopy. The analyses showed the rutile structure of the TiO2 nanowires. The photocatalytic properties were studied through the degradation of methylene blue (MB) dye under UV light irradiation. The nanowires induced an enhancement of the photo-degradation rate, compared to TiO2 in a bulk form, due to an increase in the surface area. Moreover, the presence of a nano-porous Pt layer deposited on the rear side of the samples provided a further increase in the MB degradation rate, related to the scavenging effect of Pt nanoparticles. The overall increment of the photo-activity, due to the nano-structuration of the TiO2 and to the presence of the Pt layer, resulted a factor 7, compared to the bulk reference. In addition, photovoltage measurements allowed to assess the effects of TiO2 nano-structuration and Pt nanoparticles on the electron accumulation.
| S-EPMC8232246 | biostudies-literature